Skip to contents

Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.

Setup code

To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:

library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)

plotly_widget <- plot_ly(x = diamonds$cut) %>%
  config(displayModeBar = FALSE) %>%
  layout(margin = list(t = 0, b = 0, l = 0, r = 0))

leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
  leaflet(options = .) %>%
  addTiles()

Shiny usage

Cards work equally well in Shiny. In the examples below, replace plotly_widget with plotlyOutput() and leaflet_widget with leafletOutput() to adapt them for Shiny server-rendered plots/maps.

Hello card()

A card() is designed to handle any number of “known” card items (e.g., card_header(), card_body(), etc) as unnamed arguments (i.e., children). As we’ll see shortly, card() also has some useful named arguments (e.g., full_screen, height, etc).

At their core, card() and card items are just an HTML div() with a special Bootstrap class, so you can use Bootstrap’s utility classes to customize things like colors, text, borders, etc.

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  card_body(
    markdown("Some text with a [link](https://github.com)")
  )
)
A header

Some text with a link

Implicit card_body()

If you find yourself using card_body() without changing any of its defaults, consider dropping it altogether since any direct children of card() that aren’t “known” card() items, are wrapped together into an implicit card_body() call.1 For example, the code to the right generates HTML that is identical to the previous example:

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  markdown("Some text with a [link](https://github.com).")
)
A header

Some text with a link.

Restricting growth

By default, a card()’s size grows to accommodate the size of its contents. Thus, if a card_body() contains a large amount of text, tables, etc., you may want to specify a height or max_height. That said, when laying out multiple cards, it’s likely best not to specify height on the card(), and instead, let the layout determine the height layout_column_wrap().

Although scrolling is convenient for reducing the amount of space required to park lots of content, it can also be a nuisance to the user. To help reduce the need for scrolling, consider pairing scrolling with full_screen = TRUE (which adds an icon to expand the card’s size to the browser window). Notice how, when the card is expanded to full-screen, max_height/height won’t effect the full-screen size of the card.

card(
  max_height = 250,
  full_screen = TRUE,
  card_header(
    "A long, scrolling, description"
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A long, scrolling, description

Ipsum vivamus molestie, porta justo vestibulum mi luctus fames torquent, at sollicitudin dui fermentum. Facilisi laoreet ac commodo purus sapien dignissim imperdiet. Tristique felis sollicitudin senectus ad gravida torquent curae feugiat fusce eu cursus. Dignissim nascetur porttitor, elementum luctus posuere lectus magnis dapibus enim risus tempor! Turpis torquent quam nunc cum cursus at fringilla.

Consectetur ad vulputate nullam cubilia ac habitasse molestie aliquam donec? Cubilia parturient ridiculus ante varius neque sapien id condimentum egestas. Vitae morbi urna sollicitudin risus, platea nascetur condimentum phasellus parturient sem? Convallis conubia dis auctor, felis porttitor risus pretium primis mattis libero! Sagittis montes phasellus torquent malesuada, placerat nunc per conubia?

Elit nunc eros suspendisse himenaeos sodales aenean purus mi? Turpis parturient rutrum praesent pulvinar cursus turpis sodales diam. Maecenas tincidunt tortor nam cras metus tellus scelerisque. Interdum facilisi aenean id facilisi accumsan mollis; nulla aptent sollicitudin. Sed vitae habitasse nulla accumsan, sem torquent – dui cubilia aenean.

Filling outputs

A card()’s default behavior is optimized for facilitating filling layouts. More specifically, if a fill item (e.g., plotly_widget), appears as a direct child of a card_body(), it resizes to fit the card()s specified height. This means, by specifying height = 250 we’ve effectively shrunk the plot’s height from its default of 400 down to about 200 pixels. And, when expanded to full_screen, the plot grows to match the card()’s new size.

card(
  height = 250,
  full_screen = TRUE,
  card_header("A filling plot"),
  card_body(plotly_widget)
)
A filling plot

Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny output bindings (e.g, plotOutput(), imageOutput(), etc) are fill items by default, so this behavior “just works” in those scenarios. And, in some of these situations, it’s helpful to remove card_body()’s padding, which can be done via spacing & alignment utility classes.

card(
  height = 275,
  full_screen = TRUE,
  card_header("A filling map"),
  card_body(
    class = "p-0",
    leaflet_widget
  ),
  card_footer(
    class = "fs-6",
    "Copyright 2023 RStudio, PBC"
  )
)
A filling map

Fill item(s) aren’t limited in how much they grow and shrink, which can be problematic when a card becomes very small. To work around this, consider adding a min_height on the card_body() container. For example, try using the handle on the lower-right portion of this card example to make the card taller/smaller.

This interactive example is a bit contrived in that we’re using CSS resize to demonstrate how to make plots that don’t shrink beyond a certain point, but this concept becomes quite useful when implementing page-level filling layouts (i.e., page_fillable()) with multiple cards.

card(
  height = 300,
  style = "resize:vertical;",
  card_header("Plots that grow but don't shrink"),
  card_body(
    min_height = 250,
    plotly_widget,
    plotly_widget
  )
)
Plots that grow but don't shrink

Troubleshooting fill

As you’ll learn more about in filling layouts, a fill item loses its ability to fill when wrapped in additional UI element that isn’t a fillable container. To fix the situation, use as_fill_carrier() to allow the additional element to carry the potential to fill from the card_body() down to the fill item.

Multiple card_body()

A card() can have multiple card_body()s, which is especially useful for:

  1. Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
  2. Allowing each card_body() to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g., min_height).

For example, when pairing filling output with scrolling content, you may want min_height on the filling output since the scrolling content will force it to shrink:

card(
  height = 375,
  full_screen = TRUE,
  card_header(
    "Filling plot, scrolling description"
  ),
  card_body(
    min_height = 200,
    plotly_widget
  ),
  card_body(
    class = "lead container",
    lorem::ipsum(paragraphs = 10, sentences = 5)
  )
)
Filling plot, scrolling description

Consectetur lectus per dui nullam quam rhoncus rutrum etiam urna; lectus aliquam vehicula facilisi. Dignissim sem aptent nunc cum, nec mus fermentum himenaeos fringilla integer. Nulla suspendisse est litora, mauris risus erat mauris. Sagittis dictum nisl suscipit – tellus tellus sed posuere felis faucibus. Dapibus sodales vulputate!

Consectetur mi magna praesent posuere tempor tempor netus potenti sagittis rutrum. Proin gravida a vivamus, penatibus, blandit vehicula dui. Morbi primis lacinia ornare est primis; hendrerit netus sociosqu tellus potenti. Netus leo eleifend facilisi; molestie purus habitant, nisi imperdiet; neque rutrum lacus cursus. Primis eget tristique vivamus porta cubilia euismod hac ad.

Dolor commodo taciti pretium morbi, phasellus potenti platea. Felis viverra sodales a pellentesque netus aliquet himenaeos condimentum felis. Vehicula massa integer lacus litora, tristique hac sociis hendrerit nec nulla aliquam conubia. Ullamcorper metus vulputate facilisis ridiculus sapien cum placerat commodo sociosqu tortor. Hendrerit dictumst habitasse?

Ipsum porttitor euismod vitae; eros convallis dui quam proin sollicitudin nam. Nibh congue netus habitant elementum – vestibulum libero feugiat nisl ornare aptent. Pellentesque vehicula dignissim habitant, ante sociosqu massa hac fames consequat leo volutpat senectus habitasse. Malesuada aliquam per egestas cras sociosqu. Cursus senectus nibh dictumst cras facilisis fringilla iaculis maecenas etiam; porttitor per massa velit ornare lacus interdum viverra?

Lorem taciti vel phasellus tincidunt fringilla eu nisl? Molestie nulla dignissim lacinia netus gravida nunc suscipit nibh posuere. Cubilia aliquam augue eu purus pretium curae nascetur vel. Nascetur feugiat venenatis fermentum blandit lacinia iaculis pellentesque? Praesent egestas, litora nullam justo porta mollis rutrum odio, rutrum iaculis senectus habitant, est enim porttitor nisl phasellus vehicula fermentum taciti.

Elit cras rutrum et – condimentum leo malesuada vehicula placerat? Orci laoreet arcu dui cursus lacinia cursus. Donec nostra tincidunt hac; felis a lacus. Ridiculus arcu tincidunt ornare sollicitudin tincidunt molestie curae ut convallis egestas quam. Vulputate hendrerit porttitor natoque primis vestibulum quisque ultrices taciti dapibus euismod id eget, fusce ut, auctor; risus curabitur viverra, diam sollicitudin euismod rutrum ad integer pharetra placerat pulvinar?

Consectetur platea laoreet parturient sed ultricies penatibus netus luctus phasellus imperdiet. Gravida tristique semper sem purus, augue mauris mus lectus fusce. Himenaeos blandit neque magnis congue cum lacus pharetra consequat, tristique quisque elementum. Vivamus felis inceptos quis urna mattis sodales egestas. Et vulputate suspendisse commodo venenatis pellentesque rutrum est vivamus nisl?

Sit sapien fames quis eu viverra porttitor risus inceptos felis quam ridiculus. Pellentesque ante dapibus nunc placerat tempus tempus diam. In fringilla elementum velit suscipit a risus suscipit aliquet fringilla nibh netus. Fermentum cursus pharetra augue, facilisi, penatibus ad ullamcorper semper tincidunt magnis. Purus?

Amet ultricies luctus at interdum? Libero nisi: fames ut purus facilisis ligula at. Est est porttitor convallis sociis inceptos dictumst mi porttitor vehicula. Sodales consequat et elementum, libero curae, quis inceptos platea? Lacinia ad inceptos ullamcorper pharetra taciti egestas aptent – aptent pellentesque facilisi, semper justo quis cubilia nostra purus blandit?

Ipsum ligula venenatis hac egestas torquent dignissim natoque felis? Feugiat mi malesuada aliquet – velit torquent et. Rutrum platea magna ullamcorper scelerisque fusce – eget lacus lectus. Fermentum pharetra sollicitudin, faucibus lacus morbi etiam, quis pretium mi? Velit vehicula cursus quam proin tellus eros himenaeos enim gravida – est ac neque lectus nostra facilisi sagittis tristique hac.

Also, when the content has a fixed size, and should not be allowed to scroll, set fill = FALSE:

card(
  height = 350,
  full_screen = TRUE,
  card_header(
    "Filling plot, short description"
  ),
  plotly_widget,
  card_body(
    fill = FALSE, gap = 0,
    card_title("A subtitle"),
    p(class = "text-muted", "And a caption")
  )
)
Filling plot, short description
A subtitle

And a caption

Multiple columns

As you’ll learn in column-based layouts, layout_column_wrap() is great for multi-column layouts that are responsive and accommodate for filling output. Here we have an equal-width 2-column layout using width = 1/2, but it’s also possible to have varying column widths.

card(
  height = 350,
  full_screen = TRUE,
  card_header("A multi-column filling layout"),
  card_body(
    min_height = 200,
    layout_column_wrap(
      width = 1/2,
      plotOutput("p1"),
      plotOutput("p2")
    )
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A multi-column filling layout

Adipiscing nam, leo proin duis proin rutrum mollis vulputate. Ligula metus in gravida nunc montes odio tempor venenatis porta eros posuere. Dapibus pulvinar sociis venenatis tempor: a parturient habitasse pulvinar. Lacinia consequat mi pulvinar dictum penatibus vehicula lobortis phasellus. Curae tortor curae pretium viverra quam, leo mollis felis sociosqu semper aliquet.

Amet augue praesent feugiat placerat laoreet ullamcorper et curabitur habitant facilisis praesent sollicitudin faucibus praesent taciti eu! Fusce sociosqu non nibh ultricies porta ultricies, proin mattis – aliquam dignissim. Facilisis consequat leo ultrices morbi, vestibulum suspendisse eleifend. Sodales viverra lacus aliquam fermentum. Platea tempus condimentum curabitur hendrerit ac commodo cras suscipit – quam – praesent ridiculus parturient orci.

Sit feugiat blandit justo rhoncus ut semper habitant: pharetra turpis sociosqu bibendum. Eros faucibus vel parturient neque, malesuada, pretium ut, integer quam ac rutrum parturient? Mattis nostra habitasse viverra habitant hendrerit auctor nisl, dictum tempor! Faucibus aptent fermentum ridiculus ut lacus dictum? Proin mauris sodales varius facilisi vulputate aenean?

Multiple cards

layout_column_wrap() is especially nice for laying out multiple cards since each card in a particular row will have the same height (by default). Learn more in column-based layouts.

layout_column_wrap(
  width = 1/2,
  height = 300,
  card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
  card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)
A filling plot
A filling map

Multiple tabs

navset_card_tab() and navset_card_pill() make it possible to create cards with multiple tabs or pills. These functions have the same full_screen capabilities as normal card()s as well some other options like title (since there is no natural place for a card_header() to be used). Note that, each nav_panel() object is similar to a card(). That is, if the direct children aren’t already card items (e.g., card_title()), they get implicitly wrapped in a card_body().

library(leaflet)
navset_card_tab(
  height = 450,
  full_screen = TRUE,
  title = "HTML Widgets",
  nav_panel(
    "Plotly",
    card_title("A plotly plot"),
    plotly_widget
  ),
  nav_panel(
    "Leaflet",
    card_title("A leaflet plot"),
    leaflet_widget
  ),
  nav_panel(
    shiny::icon("circle-info"),
    markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
  )
)
HTML Widgets
A plotly plot
A leaflet plot

Learn more about htmlwidgets

As you’ll learn more about in sidebar layouts, layout_sidebar() just works when placed inside in a card(). In this case, if you want fill items (e.g., plotly_widget) to still fill the card like we’ve seen before, you’ll need to set fillable = TRUE in layout_sidebar().

card(
  height = 300,
  full_screen = TRUE,
  card_header("A sidebar layout inside a card"),
  layout_sidebar(
    fillable = TRUE,
    sidebar = sidebar(
      actionButton("btn", "A button")
    ),
    plotly_widget
  )
)
A sidebar layout inside a card

Static images

card_image() makes it easy to embed static (i.e., pre-generated) images into a card. Provide a URL to href to make it clickable. In the case of multiple card_image()s, consider laying them out in multiple cards with layout_column_wrap() to produce a grid of clickable thumbnails.

card(
  height = 300,
  full_screen = TRUE,
  card_image(
    file = "shiny-hex.svg",
    href = "https://github.com/rstudio/shiny"
  ),
  card_body(
    fill = FALSE,
    card_title("Shiny for R"),
    p(
      class = "fw-light text-muted",
      "Brought to you by RStudio."
    )
  )
)
Shiny for R

Brought to you by RStudio.

Flexbox

Both card() and card_body() default to fillable = TRUE (that is, they are CSS flexbox containers), which works wonders for facilitating filling outputs, but it also leads to surprising behavior with inline tags (e.g., actionButton(), span(), strings, etc). Specifically, each inline tag is placed on a new line, but in a “normal” layout flow (fillable = FALSE), inline tags render inline.

card(
  card_body(
    fillable = TRUE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn1", "A button")
  ),
  card_body(
    fillable = FALSE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn2", "A button")
  )
)
Here's some inline text
Here's some inline text

That said, sometimes working in a flexbox layout is quite useful, even when working with inline tags. Here we leverage flexbox’s gap property to control the spacing between a plot, a (full-width) button, and paragraph. Note that, by using markdown() for the paragraph, it wraps the results in a <p> tag, which means the contents of the paragraph are not longer subject to flexbox layout. If we wanted, we could do something similar to render the actionButton() inline by wrapping it in a div().

card(
  height = 325, full_screen = TRUE,
  card_header("A plot with an action links"),
  card_body(
    class = "gap-2 container",
    plotly_widget,
    actionButton(
      "go_btn", "Action button",
      class = "btn-primary rounded-0"
    ),
    markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
  )
)
A plot with an action links

Here's a simple hyperlink.

In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.

card(
  height = 300, full_screen = TRUE,
  card_header(
    class = "d-flex justify-content-between",
    "Centered plot",
    checkboxInput("check", " Check me", TRUE)
  ),
  card_body(
    class = "align-items-center",
    plotOutput("id", width = "75%")
  )
)
Centered plot

Shiny

Since this article is statically rendered, the examples here use statically rendered content/widgets, but the same card() functionality works for dynamically rendered content via Shiny (e.g., plotOutput(), plotlyOutput(), etc).

An additional benefit that comes with using shiny is the ability to use getCurrentOutputInfo() to render new/different content when the output container becomes large enough, which is particularly useful with card(full_screen = T, ...). For example, you may want additional captions/labels when a plot is large, additional controls on a table, etc (see the value boxes article for a clever use of this).

# UI logic
ui <- page_fluid(
  card(
    max_height = 200,
    full_screen = TRUE,
    card_header("A dynamically rendered plot"),
    plotOutput("plot_id")
  )
)

# Server logic
server <- function(input, output, session) {
  output$plot_id <- renderPlot({
    info <- getCurrentOutputInfo()
    if (info$height() > 600) {
      # code for "large" plot
    } else {
      # code for "small" plot
    }
  })
}

shinyApp(ui, server)

Appendix

The following CSS is used to give plotOutput() a background color; it’s necessary here because this documentation page is not actually hooked up to a Shiny app, so we can’t show a real plot.

.shiny-plot-output {
  background-color: #216B7288;
  height: 400px;
  width: 100%;
}